AVAudioEngine MIDI file play (Current progress + MIDI end callback) Swift - swift

Question

Am playing MID using AVAudioEngine, AVAudioSequencer, AVAudioUnitSampler.
AVAudioUnitSampler loads Soundfont and AVAudioSequencer load MIDI file.
My initial configurations are
engine = AVAudioEngine()
sampler = AVAudioUnitSampler()
speedControl = AVAudioUnitVarispeed()
pitchControl = AVAudioUnitTimePitch()
engine.attach(sampler)
engine.attach(pitchControl)
engine.attach(speedControl)
engine.connect(sampler, to: speedControl, format: nil)
engine.connect(speedControl, to: pitchControl, format: nil)
engine.connect(pitchControl, to: engine.mainMixerNode, format: nil)
Here is how my sequence loads MIDI file
func setupSequencer() {
self.sequencer = AVAudioSequencer(audioEngine: self.engine)
let options = AVMusicSequenceLoadOptions()
let documentsDirectoryURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
let introurl = URL(string: songDetails!.intro!)
let midiFileURL = documentsDirectoryURL.appendingPathComponent(introurl!.lastPathComponent)
do {
try sequencer.load(from: midiFileURL, options: options)
print("loaded \(midiFileURL)")
} catch {
print("something screwed up \(error)")
return
}
sequencer.prepareToPlay()
if sequencer.isPlaying == false{
}
}
And here is how sampler load SoundFont
func loadSF2PresetIntoSampler(_ preset: UInt8,bankURL:URL ) {
do {
try self.sampler.loadSoundBankInstrument(at: bankURL,
program: preset,
bankMSB: UInt8(kAUSampler_DefaultMelodicBankMSB),
bankLSB: UInt8(kAUSampler_DefaultBankLSB))
} catch {
print("error loading sound bank instrument")
}
}
And it's playing fine no issue with this. I have 2 other requirements, and am having problem in those
I have to play another MIDI file after first MID ends playing, for that i need to get the complete/finish MIDI file callback from either Engine or Sequence OR How can i load multiple MIDI files in Sequence? I have tried many ways but didn't help.
I need to show the progress of MIDI file play, like current time and total time. For this i have tried a method found in stack answers somewhere which is:
var currentPositionInSeconds: TimeInterval {
get {
guard let offsetTime = offsetTime else { return 0 }
guard let lastRenderTime = engine.outputNode.lastRenderTime else { return 0 }
let frames = lastRenderTime.sampleTime - offsetTime.sampleTime
return Double(frames) / offsetTime.sampleRate
}
}
Here offsetTime is
offsetTime = engine.outputNode.lastRenderTime
And it always return nil.

Answer 1

Glad to see someone using my example code.
It's a missing feature. Please file a Radar. Nothing will happen without a Radar.
They do pay attention to them to schedule what to work on.
I fake it by getting the length of the sequence.
if let ft = sequencer.tracks.first {
self.lengthInSeconds = ft.lengthInSeconds
} else {
self.lengthInSeconds = 0
}
Then in my play function,
do {
try sequencer.start()
Timer.scheduledTimer(withTimeInterval: self.lengthInSeconds, repeats: false) {
[weak self] (t: Timer) in
guard let self = self else {return}
t.invalidate()
self.logger.debug("sequencer finished")
self.sequencer.stop()
}
...
You can use a DispatchSourceTimer if you want more accuracy.